1. Field of the Invention
This invention relates to an improved structure for positive clutches of the type comprising a first clutch member fixed for rotation, with a degree of rotational freedom, to a first rotatable device and selectively engagable with a second clutch member rotatable with a second rotatable device.
More particularly, the present invention relates to the distribution of backlash, or rotational freedom, between the clutch system members of a positive clutch system.
2. Description of the Prior Art
Positive clutch systems for selectively rotationally coupling and decoupling a first rotatable device, such a gear, to a second rotatable device, such as a shaft, are, of course, well known in the prior art. Change gear transmissions utilizing such positive clutches, without synchronizing mechanisms to minimize the cost, size and/or complexity thereof, are well known in the prior art as may be seen by reference to U.S. Pat. Nos. 2,951,395; 3,105,395; 3,335,616; 3,500,695; 3,799,002 and 4,388,838, the disclosures of which are hereby incorporated by reference.
The clutch members of nonsynchronized positive clutch systems are, preferably, provided with clutch teeth having a leading edge structure which, during a clutch engagement, will tend to cause the clutch members to ratchet rather than engage if the relative rotational speeds thereof exceed a predetermined value. An example of such a clutch tooth structure may be seen by reference to U.S. Pat. No. 3,265,173, the disclosure of which is hereby incorporated by reference. As is known, for a given engagement force, the maximum allowable relative rotational speed at which the positive clutches will properly engage (i.e. sufficient clutch tooth penetration will occur) is a directly proportional function of the total effective backlash in the clutch system. The maximum allowable asynchronous conditions at which clutch engagement is allowed is selected in view of the most harsh clutch engagement which is acceptable.
While change gear transmissions utilizing the nonsynchronized positive clutch structures of the prior art, especially for heavy duty vehicles, are very commercially successful, such transmissions and clutch structures are not totally satisfactory as, for a given total backlash, i.e. a given maximum allowably harsh clutch engagement, the range of asynchronous conditions at which the clutch members will engage is narrower than desirable making shifting more difficult.